If you manage to hose it up while in the process of jail breaking/unlocking, you're S.O.L.
The kind folks at Apple will very politely tell you to pound sand.
Successful or not, you void the warranty the moment you alter the OS/Base band/Firmware.
Are you sure you "F'ed" it up with pwnage tool? It is almost impossible to do because everything you do to the baseband with it is completely reversible.
Are you sure you "F'ed" it up with pwnage tool? It is almost impossible to do because everything you do to the baseband with it is completely reversible.
If you do not unlock it and only jailbreak it then you will be fine 99.99%. If you only jailbreak you should always be able to hit the restore button in iTunes and start from scratch again. Unlocking and then updating is the only thing that could harm your phone.